This invention relates to the manufacture of blown glass articles such as bottles, jars, flasks, etc. According to the "narrow neck blow and blow" , method presently used and as described in U.S. Pat. No. 1,911,119, a charge of glass is delivered to and compacted or caused to settle in the cavity of an inverted or neck-down, blank or parison mold. The glass of the charge will be extending from the neck portion of the mold cavity, part of the way up the sides thereof. A baffle is placed on the uppermost end of the inverted blank or parison mold and air under pressure is applied to the interior of the glass in the mold through the neck opening to counterblow such glass into conformity with the internal configuration of the blank or parison mold and against the baffle. Thereafter, the counterblown blank or parison is transferred to an upright final blow mold in which the blank or parison is disposed in an upright or neck-up position and air under pressure is applied to the interior thereof. The counterblown blank or parison is thus expanded to the configuration of the final blow mold cavity, thereby forming an article of the final shape and size desired.
This method of forming articles of glassware has been practices since the 1920's. Certain faults and shortcomings have been known and such defects as "settle waves" in the sidewalls of the article, marking the juncture of wall portions of two different thicknesses are common. Furthermore, articles of generally circular cross-sectional configuration have experienced the formation of excessively thick shoulders and relatively thin bottoms when produced by the above-described method. Those articles which would have a generally rectangular cross-sectional configuration or are of a flask shape usually have excessively thick sides or panels and relatively thin corner sections. As a matter of fact, different portions of practically all articles produced by the aforementioned method vary substantially in the thickness of the walls thereof. Therefore, for most articles of a given size and intended use, it has been necessary to use a glass charge of undue size and weight so as to insure that the article produced will be thick, and therefore strong, enough at its thinnest wall portion to enable the article to withstand the normal filling line abuse and later handling in the service for which the article is intended. A smaller charge could be used if better glass distribution were effected in the forming process resulting in a saving of material and energy.
An attempt to avoid some of the problems discussed above would appear to have formed the basis for U.S. Pat. No. 1,840,532 dated Jan. 12, 1932, issued to C. E. Rowe. The general teaching of this patent was, in effect, that if the making of a bottle could be accomplished without forming a parison in a parison mold, then a lighter weight bottle could be produced. Whether this patent or the invention set forth therein ever became commercially significant or was ever actually practiced is not known to applicants. It is clear that the previously mentioned U.S. Pat. No. 1,911,119 issued to the same assignee, has become the forerunner of the presently successful and commercially important standard "I.S." glass forming machine. One complicating factor that was involved, in the preocess of Rowe, was the rotation of the charge of glass about the central axis of the neck mold, in order to attain some semblance of even distribution of the glass about the bubble that was being blown or formed therein. This would appear to be a closer approach to the hand-blowing techniques where the charge was rotated by the glass blower on the end of a punty while being expanded.
Some of the shortcomings and faults mentioned above are eliminated or their effect is minimized by the present invention which , it will be seen from the detailed description to follow, has some of the steps of the well-known, commonly practiced, "blow and blow" process of forming glassware, but will differ therefrom in important particulars.
It has been known that hand-blowing techniques for forming hollow objects from glass have been capable of producing thin walled articles having fairly uniform wall thickness. The hand-blowing technique, however, requires considerable skill and experience and in this day is a relatively unique talent not possessed by many glass producers and certainly would not be an economical method of producing glass containers of the type that are presently made by machines in large volume.
In addition to the foregoing description of published information respecting the well-known "blow and blow" process, a co-pending U.S. Patent application Ser. No. 775,131, filed Mar. 7, 1977, of common assignee, sets forth a glass forming process in which the "parison" is formed by a vacuum settle followed by the counterblowing of glass in the parison mold, with the formed parison having the thermal characteristic that in order to invert the parison, it is necessary to maintain a superatmospheric pressure within the parison.